DE3113681A1 - Fixed venturi-carburettor for internal combustion engines - Google Patents

Abstract

In a fixed venturi-carburettor for internal combustion engines, the main system (7) and the idling system (8) are combined into a single system, in that the lines (9, 12) connecting the nozzles (10, 13) of these individual systems to the float chamber (24) are combined into a common line (16), the flow cross-section of which is controlled mechanically or electrically by a fuel metering device (18, 19) at least as a function of the position of the main throttle (3). The nozzles (10, 13) of the individual systems have a relatively large flow cross-section and the fuel metering device (18, 19) ensures a reduction of the upstream flow cross-section as a function of the operation, especially when idling. The pressure of the mixture prevailing in the lines (9, 12) of the individual systems and increasing only slightly as the load increases permits, in conjunction with the fuel metering device (18, 19) to be opened as the load increases or the main throttle (3) opens, a proportional relationship between the fuel intake quantity and the rate of air flow and thereby a smooth pick-up over the entire operating range with only a single system. In the case of a mechanical control of the fuel metering device (18, 19), an electronically controllable enrichment line (26) for cold starting is provided, opening into the common line (16) downstream of this device. An electronically controllable correction air duct (30), opening into the common line (16) downstream of the fuel metering device (18, 19), serves for varying the air-fuel ratio. <IMAGE>

Description

The invention relates to a fixed air funnel carburetor

for internal combustion engines with a first nozzle about in the narrowest Venturi area upstream of a main throttle opening into an intake pipe Main system, which is connected to a float chamber via a first line, and with one opening into the intake pipe via a second nozzle downstream of the main throttle Idle system that is connected to the float chamber via a second line.

Such a fixed-air funnel carburetor of known type has one another separate main and idle systems, from which, for example, the disadvantage shows that the transfer of operations from the idle system to the main system resp. when inserting the main system easily a driving error in the form of a jerky one Operating mode results. If a correction of the main and idle mixtures is desired this must be done separately in both systems. In this context For example, a carburetor is known that operates in the main system and in the idle system each contains an electric control valve. This solution is complex and can also lead to driving errors.

From the German utility model 79 18 875 it is known in a Fixed air funnel carburetor in addition to a main and an idle system to provide a correction system independent of this, on the one hand via a nozzle roughly in the narrowest Venturi area and on the other hand via a nozzle into the intake pipe opens downstream of a main throttle. The fuel is dependent on a valve clocked by the signal of an exhaust pipe oxygen probe and one of these downstream nozzle fed to a branch of this correction system, which via the mentioned nozzles in the venturi area as well into the suction pipe flows out. In the branching of the correction system, therefore, it always occurs Mixing pressure between the intake manifold negative pressure prevailing downstream of the main throttle and the negative pressure prevailing in the venturi area. These negative pressures are over the operating range in opposite directions. When the main throttle is closed, the fuel is practically only sucked into the intake manifold downstream of the same, with that in the venturi area the opening part of the branch acts as a ventilation. With increasing Luit throughput, so when the main throttle is opened, the negative pressures in the venturi area increase and in the suction pipe.

The ventilation via the part of the correction system that opens into the venturi area becomes lower, and the differential pressure at the nozzle assigned to the solenoid valve increases. This should allow the fuel throughput over the entire operating range adjusted so that the fuel addition of the correction or attachment system increases progressively with the air throughput. This carburetor has the basic one Disadvantage that it is relatively complex and several independent from each other Systems such as the main system, the idle system, and the correction system. The correction system, which works according to the mixing principle, only enables one 40 fuel allocation maximum, with the remaining systems taking the remaining fuel have to allocate.

The present invention is based on the object of a fixed air funnel carburetor of the type mentioned so that he can avoid the described Disadvantages of a simple and inexpensive structure with as little system effort as possible works flawlessly and a driving error-free sweeping of the entire operating area enables.

A fixed air funnel carburetor is used to solve the problem of the type mentioned in the preamble according to the invention by combining the first and second conduits between the float chamber and a conduit branch upstream of the first and second nozzles to a common third conduit a third nozzle in the common third conduit, through one of the third nozzles assigned, position-variable metering element for changing the free flow cross-section the third line and through a metering member depending at least on the position of the main throttle actuating actuator.

Such a carburetor allows with only a single, combined System a fuel supply proportional to the air flow in all operating ranges. Such a 100% fuel allocation with only one system leads to a considerable Simplification of the entire structure as well as the functioning of the carburetor and to a driving error-free sweeping of the entire operating range from idling up to full load operation under different operating conditions. Similar to that Correction system of the carburetor according to the German utility model 79 18 875 here, but in connection with the main system and the idle system, the all fuel is supplied downstream of the main throttle element closed, the line opening into the venturi area serves as ventilation. With increasing When the main throttle is opened, i.e. with increasing air throughput, the negative pressure increases in the venturi area, until finally a negative pressure and flow reversal takes place and all of the fuel is drawn into the vent.

This can be done via the line opening into the suction pipe one Air backflow take place. The negative pressures are in a medium load range the same size in the air funnel and in the intake pipe, so that fuel comes from both lines exit. Since with increasing air throughput, i.e. with increasing opening of the main throttle organ, the negative pressure in the air funnel increases and the negative pressure in the suction pipe downstream of the main throttle body decreases, results in the from the first to third lines existing pipe system depending on the dimensioning of the first and second nozzles a mixed pressure that increases slightly with increasing air throughput.

A desired proportionality between the amount of fuel and the air throughput, however, a quadratic negative pressure or mixed pressure curve is required, which, however, cannot be achieved with the mentioned nozzles.

In the context of the present invention it was found that a Correction of the fuel allocation thus required is only possible in that with sufficiently large first and second nozzles, the flow cross-section in the common third line depending on the position of the main throttle body is changed. Accordingly, this flow cross-section is reduced when idling, to prevent too much from having a relatively large second nozzle Fuel is drawn into the intake pipe. With increasing load, the flow cross-section becomes increased, so that finally comparatively more fuel in the at full load Air funnel can enter. This eliminates the incline of the mixing pressure curve, which is in itself too small compensated and a strict proportionality between the amount of fuel as well forced air flow, although only a single combined system is used comes.

In a simple embodiment, an actuator with a mechanical implementation of the position of the main throttle in the respective position of the Dosing member used. In this context, the main throttle can be connected to the metering member connecting rods are used. The construction of such a carburetor is simple, inexpensive and reliable.

In the case of a mechanical implementation, the position of the main throttle In the position of the metering member, it is preferred to use an additional enrichment system to be provided for low-temperature cold starts, as a there is a fixed connection between the positions of the individual members and at there is an increased fuel requirement at very low temperatures. Serves this purpose an enrichment line opening into the common third line downstream of the third nozzle with an electric enrichment valve that can be opened during low-temperature cold starts. This is preferably carried out by an electronic control unit as a function of actuated at least one operating parameter. This correction device thus occurs in function only in borderline cases, while in normal operation the entire fuel allocation exclusively through the changeable mixing pressure and the changeable flow cross-section the common third line takes place.

A particularly preferred alternative to the mechanical conversion system Embodiment has an actuator with an electrical conversion of the position the main throttle in the respective position of the metering member. Preferably be an electronic control unit with at least an operating parameter input for the position of the main throttle and an electrical one operated by the control unit Motor used to adjust the metering member. Such an electrical conversion system has considerable advantages over a purely mechanical implementation. As a mechanical one Conditional compulsory relationship between the position of the main throttle and the position of the dosing member is missing, the dosing member can be adjusted so that further correction values taken into account or operating conditions are met. This makes it possible for example on the separate enrichment system for low-temperature cold starts to do without, since the dosing member to start the engine at a very low temperature can be opened wider than normal. Accordingly, such a carburetor is with a simpler structure, more versatile to adapt to the various operating conditions. For these and other adaptation tasks, it can be useful to use the electronic Control unit with further operating parameter rings for the engine speed and the Form suction pipe pressure so that the position of the metering member is corrected accordingly can be.

In a further embodiment, a downstream of the third nozzle into the Third line leading to the correction air channel with a controllable correction air valve intended. The valve can be controlled by an electronic control unit of operating parameters, such as during a cold start, in the warm-up phase and possibly in Characteristic map, are operated. Thus, by means of the correction air, relative simply adjust the air-fuel ratio as required to the respective operating conditions adjust. To make the structure as simple as possible to get, can have an additional control connection in the case of the mechanical conversion system between the electronic control unit and the enrichment valve. In contrast, the electrical conversion system can have an additional control connection between the electronic control unit and the electric motor for the metering member are provided. In this way, the structural effort can be reduced by multiple use of the electronic control unit. This also results in a easier coordination between the individual control tasks.

In a further expedient embodiment, the first and / or second nozzles adjustable in their free flow cross-sections. This can the course of the mixed pressure in the first to third lines between the first up to third nozzles can be influenced and thus optimally adjusted; this includes Such a setting that the mixing pressure depends on the air flow in the same sense and as close as possible to a quadratic course changes. The resulting deviation from the quadratic dependence is then corrected during operation by adjusting the metering member.

To improve the mixture distribution, it is also preferred to use a Main system and / or an idle system with one of the first and second lines, respectively connected to provide the main flow path surrounding annular channel, the circumferential Distributed inlet channels in the main flow path, that is, in the narrowest Venturi area or into the suction pipe. This enables an optimal circumferential mixture distribution can be achieved in the main flow path. Such a ring channel is especially for that second Line important, i.e. for idling, and in the lower speed range, because all the fuel from idling to full load comes exclusively from the second line exits. Regardless of this, however, a corresponding one also leads Ring channel in the area of the air funnel for more favorable mixture distribution as well Operational characteristics.

In principle, it is also possible to have a main system with one in the venturi area Provide anoraneten pre-atomizer, in which the first line via the first nozzle joins. This results in good atomization and mixture distribution in a manner known per se achieved.

It can be applied to an enrichment system or to a correction air valve can be omitted if, in a further embodiment, an electronically controlled Pre-throttle upstream of the mixing chamber to correct the air-fuel ratio, for the cold start, for the warm-up and possibly in the map. By adjusting the choke accordingly, the various operating conditions can also be met without the aforementioned additives.

The fixed air funnel carburetor according to the invention allows with one single system and a single controllable metering element a needs-based Fuel allocation over the entire operating range without the known Carburetors common driving errors occur. By adapting the metering element accordingly, For example, the contour of a needle, all allocation conditions can be set meet so that separate no-load, additional, bypass, partial load enrichment and full load enrichment systems can be omitted. While normally there is a pre-throttle upstream of the mixing chamber, this can in principle here omitted if a corresponding control of the cold start and the warm-up, for example by means of a cold start valve and a separate warm-up valve.

The invention is illustrated below with reference to the drawings Embodiments explained in more detail. They show: FIG. 1 in a schematic longitudinal section a carburetor with a mechanical implementation of the position of a main throttle in the position of a dosing member; Fiz. 2 the carburetor of FIG. 1 in a schematic Side view to illustrate a connecting a main throttle with a metering member mechanical linkage; 5 shows an embodiment in a schematic longitudinal section a carburetor with an electrical implementation of the position of the main throttle in the position of the dosing member; and FIG. 4 shows a further embodiment of one according to the invention Carburetor with ring channels and circumferentially distributed inlets in the venturi area as well as downstream of the main throttle.

According to Figure 1, a pipe wall 1 surrounds an unspecified Main flow path of a fixed-air funnel carburetor. A mixing chamber 2 is downstream from a main throttle 3 in the form of a pivoting throttle valve limited. In the upstream area of the mixing chamber 2 there is a Reduced cross-section air funnel or venturi area 4, through the from the inlet area 5 of the carburetor air sucked in via the mixing chamber 2 into an intake pipe 6 downstream the main throttle 3 flows.

Upstream of the venturi area 4 can be in the inlet area 5 of the carburetor a pre-throttle (not shown) that is similar to the main throttle 3 can be designed as a pivotable flap.

The carburetor has a venturi opening 4 into the narrowest venturi area and the main system 7 serving for fuel allocation at least in full load operation as well as an idling system opening into the intake pipe 6 downstream of the main throttle 3 8, that for a fuel allocation in the intake pipe 6 at least in idle mode and ensures in partial load operation.

The main system 7 has a first line 9, which has a first The nozzle 10 opens into the pre-atomizer 11 arranged centrally in the venturi area 4. The idling system 8 has a second line 12 which passes through a second nozzle 13 opens into the suction pipe 6. In the illustrated embodiment, the free The flow cross section of the second nozzle 13 can be changed by means of an adjusting screw 14, which carries a dispensing needle engaging in the second nozzle 13 at the free end. the first and second lines 9 and 12 have a common starting point at one Line branch 15 into which a common third line 16 opens. These is via a third nozzle 17 in a dip tube 23 with a float chamber 24 tied together. A longitudinally displaceable metering member 18 with a metering member located at the free end, unspecified metering needle is via an arm 19, one articulated thereon Connecting rod 20 as well as a lever 21 articulated thereon a pivot shaft 22 of the main throttle 3 is connected. The arrangement is such that the pivoting movement of the main throttle 3 into a linear movement of the metering member 18 is implemented, the free flow cross section of the third nozzle 17 with increasing degree of opening of the main throttle 3 is increased. The float chamber 24 is via a float chamber ventilation 25 with the inlet area 5 of the carburetor tied together.

The fuel throughput depends on Bernoulli's law of flow on the pressure difference and the free flow cross-section. To be a constant Air-fuel ratios, including when idling, are obtained throughout Characteristic map, defined pressure differences and defined cross-sections required. Of the Negative pressure in the first to third lines 9, 12, 16 depends on the negative pressure in the venturi area 4 and in the intake pipe 6. According to the selection of the first and second nozzles 10, 13 you can see the mixed pressure curve in these lines determine different air flow rates. Since the negative pressure in the venturi area 4 with increasing air throughput increases, while the negative pressure in the intake pipe 6 increases with If the air throughput decreases, the result is a gradually increasing one with the air throughput Mixed pressure. The gradient of the mixed pressure curve does not have a quadratic course, like it for a proportionality between the amount of fuel and the air flow would be necessary. To establish this proportionality, in connection with relative large first and second nozzles 10, 13 the free flow cross-section of the third When idling, nozzle 17 is reduced accordingly so as not to get too much fuel into the To let the intake pipe enter. With an increasing degree of opening of the main throttle 3 the free flow cross-section of the third nozzle 17 is increased. This is done by the changed position of a conical dosing needle of the dosing member 18 this free flow cross-section varies at different load points. By Adjusting the needle contour can achieve the desired air-fuel ratio achieved at every air flow rate (load point) or at every position of the main throttle will.

Essentially all of the fuel reaches the full load range via the second nozzle 13 into the suction pipe 6, the first line 9 with the first Nozzle 10 serves as a ventilation. As the degree of opening of the main throttle 3 increases, it increases the negative pressure in the venturi area 4 finally increases so far that this negative pressure is equal to the negative pressure in the intake pipe 6. In this case, pure fuel occurs from both nozzles 10 and 13. If the main throttle 3 is opened further, a The flow is reversed and the fuel only emerges from the first nozzle 10. Here the second line 12 can work with the second nozzle 13 as a ventilation, so that a return flow of air from the intake pipe 6 via the second line 12 takes place.

In a carburetor of the type shown in Figures 1 and 2 results a fixed assignment between the Positions of the main throttle 3 and the metering element 18. For low-temperature cold starts an enrichment system must therefore be in place, which in this case is a In the float chamber 24 guided accumulation line 26 has. This flows out into the common third line 16 and is at the mouth with an enrichment valve 27 provided, which is operated by an electronic control unit 28, the over Inputs 29 at least one operating parameter, such as a temperature parameter, and optionally further parameters such as engine speed and intake manifold pressure can be entered.

The enrichment valve 27 is opened for low-temperature cold starts, and possibly with temperature-controlled degree of opening, so that over the Enrichment line 26 additional fuel into the third line 16 and thus can get into the main flow path.

The common third line 16 opens downstream of the third nozzle 17 also has a correction air duct 30 which is closed by a correction air valve 31 or can be opened as required. Accordingly, there is a correction air supply a change in the air-fuel ratio during a cold start, in the warm-up phase and possibly possible in the map. The supply of correction air also has the The advantage that this improves the fuel transport through the lines can. In the present case, the correction air valve 31 is also with the electronic one Control unit 28 connected, which is thus used to actuate the enrichment valve 27 and of the correction air valve 31 is used twice.

In the embodiment of Figure 3, those of the embodiment carburetor parts corresponding to FIGS. 1 and 2 with the same reference numerals proven; in this respect, reference is made to the description above. The carburetor after Figure 3 differs from the carburetor described above in that here an electrical conversion of the position of the main throttle 3 into the position of the metering member 18 takes place. For this purpose, an electronic control unit 33 has inputs 34 at least one representing the respective opening position of the main throttle 3 Input signal from which the electronic control unit 33, possibly in connection with further entered operating parameters, such as the intake manifold pressure and the engine speed, a position signal for an electric motor 32 moving the metering member 18 generated. In this system there is thus not necessarily a fixed relationship between the position of the main throttle 3 and the position of the dosing member 18. For this reason, it is possible in the embodiment according to 3 to dispense with the enrichment system according to FIGS. 1 and 2. In Depending on the operating parameters entered, the electronic Control unit 33 this enrichment via an additional adjustment of the dosing member 18 make. In the embodiment shown in Figure 3, the electronic Control unit 33 at the same time for controlling the correction air valve 31, see above that here, too, there is a related double use of the electronic component.

As can be seen from Figure 4, the first line 9 via the first nozzle 10 into an annular channel 35 surrounding the venturi region 4 in the pipe wall 1 flow. This annular channel 35 in turn opens out via circumferentially distributed inlet channels 36 into the Venturi region 4. The second line 12 opens out in a similar manner the second nozzle 13 into a surrounding the intake pipe 6 downstream of the main throttle 3 Annular channel 37, which in turn via circumferentially distributed inlet channels 38 into the Intake pipe 6 opens. This makes it possible to have a much better mixture distribution to achieve. This is particularly important for idling and the lower speed range, when the fuel through the second line 12 and the second nozzle 13 is exclusive reaches the area downstream of the main throttle 3. The other carburetor parts of the The embodiment according to FIG. 4 corresponds to the embodiments according to the figures 1 and 2 and FIG. 3 and, where shown, have corresponding reference numerals occupied, so that in this context reference is made to the preceding description can be.

While normally in the various embodiments one upstream of the venturi region 4, not shown, pre-throttle is present is, this can be omitted if the cold start and the warm-up with the appropriate Cold start and warm-up valves are controlled. It is also possible to have one electronically controlled throttle to be used to correct the air-fuel ratio for the cold start, the warm-up and possibly in the map as well as for low-temperature cold starts is controlled accordingly. In this case you can also use the correction air valve 31 with the correction air duct 30 and the enrichment valve 27 with the enrichment line 26 are not applicable.

In principle it is of course possible with the help of the correction air valve 31 and of the electronic control unit 28 or 33, in addition, a lambda correction respectively.

- to make arrangements, if this is desired. By the way, it can Correction air valve 31 have a minimum air throughput - what the fuel transport favored -and gradually opened during the warm-up to lean the mixture.

The illustrated embodiments are only exemplary and can be modified in various ways within the scope of the present invention will. It is important, however, that a single, combined allocation system with a single, controllable metering element for a driving error-free sweeping of the entire operating area is used. The variable position metering element is operated depending on the position of the main throttle and ensures that that taking into account the deviating from a quadratic course Mixed pressure nevertheless a strict proportional-.

between the amount of fuel and the air flow. A Such a carburetor has a simple structure, is inexpensive, robust and has great operational reliability easy to adjust.

Claims (17)

"Fixed air funnel carburettor for internal combustion engines" patent claims: Fixed air funnel carburetor for internal combustion engines with a first nozzle for example in the narrowest Venturi area upstream of a main throttle in an intake pipe opening main system, which is connected to a float chamber via a first line is, and with one via a second nozzle downstream of the main throttle in the intake pipe draining idling system that is connected to the float chamber via a second line is a union of the first and second Lines (9, 12) between the float chamber (24) and a line branch (15) upstream of the first and second nozzles (10, 13) to a common dri.-l, teii Line (16), through a third nozzle (17) in the common third line (16), by a position-variable metering element (18) assigned to the third nozzle (17) for changing the free flow cross-section of the third line (16) and through a metering member (18) as a function of at least the position of the main throttle (3) actuating actuator (19, 20, 21; 32, 33). 2. Carburetor according to claim 1, g e k e n n z e i c h n e t d u r c h an actuator (19, 20, 21) with a mechanical implementation of the position of the main throttle (3) in the respective position of the metering member (18). 3. Carburetor according to claim 2, g e k e n n z e i c h n e t d u r c h a linkage (19, 20) connecting the main throttle (3) to the metering member (18), 21). 4. Carburetor according to one or more of claims 1 to 3, g e k An additional enrichment system (26, 27) for Low temperature cold starts, 5. Carburetor according to claim 4, g e k e n n z e i c h n e t d u r c h one downstream of the third nozzle (17) into the common third line (16) opening enrichment line (26) with a low-temperature cold start Electric enrichment valve to be opened (27). 6. Carburetor according to claim 5, g e k e n n z e i c h n e t d u r c h the enrichment valve (27) as a function of at least one operating parameter actuating electronic control device (28). 7. Carburetor according to claim 1, g e k e n n z e i c h n e t d u r c h an actuator (32, 33) with an electrical conversion of the position of the main throttle (3) in the respective position of the metering member (18). 8. Carburetor according to claim 7, ge k e n n z e i c h n e t d u r c h an electronic control unit (33) with at least one operating parameter input (34) for the position of the main throttle (3) and by one of the control unit (33) actuated electric motor (32) for Varstellen the dosing member (18). 9. Carburetor according to claim 8, g e k e n n z- e i c h n e t d u r c h further operating parameter inputs (34) of the electronic control unit (33) for the engine speed and the Manifold pressure. 10. Carburetor according to one or more of claims 1 to 9, g e k E n n z e i c h n e t d u r c h one downstream of the third nozzle (17) into the third Line (16) opening correction air channel (30) with a controllable correction air valve (31). 11. Carburetor according to claim 10, g e k e n n z e i c h n e t d u r c h a correction air valve (31) as a function of operating parameters, such as during a cold start, in the warm-up phase and possibly in the map, actuating electronic Control unit (28; 33). 12. Carburetor according to claim 11, g e k e n n z e i c h n e t d u r c h an additional control connection between the electronic control unit (28) and the enrichment valve (27). 13. Carburetor according to claim 11, g e k e n n z e i c h n e t d u r c h an additional control connection between. the electronic control unit (33) and the electric motor (32) for the metering member (18). 14. Carburetor according to one or more of claims 1 to 13, g e no indi cations can be set in their free flow cross-sections first and / or second nozzles (10, 13). 15. Carburetor according to one or more of claims 1 to 14, g e no indication of a main system (7) and / or an idle system (8) with a main flow path connected to the first or second line (9 or 12) surrounding annular channel (35 or 37), the circumferentially distributed inlet channels (36 or 38) in the main flow path, i.e. in the narrowest Venturi area (4) or in the suction pipe (6) opens. 16. Carburetor according to one or more of claims 1 to 15, g e a main system (7) with one in the venturi area (4) arranged pre-atomizer (11), into which the first line (9) via the first The nozzle (10) opens. 17. Carburetor according to one or more of claims 1 to 16, g e no e c h n e t d u r c h an electronically controlled pre-throttle upstream the mixing chamber to correct the air-fuel ratio, for cold starts, the warm-up and possibly in the map.